tap: Improve -netdev/netdev_add/-net/... tap error reporting

When -netdev tap fails, it first reports a specific error, then a
generic one, like this:

    $ qemu-system-x86_64 -netdev tap,id=foo
    qemu-system-x86_64: -netdev tap,id=foo: could not configure /dev/net/tun: Operation not permitted
    qemu-system-x86_64: -netdev tap,id=foo: Device 'tap' could not be initialized

With the command line, the messages go to stderr.  In HMP, they go to
the monitor.  In QMP, the second one becomes the error reply, and the
first one goes to stderr.

Convert net_init_tap() to Error.  This suppresses the unwanted second
message, and makes the specific error the QMP error reply.

[Dropped duplicate "and" from error message as suggested by Eric Blake:
"ifname=, script=, downscript=, and vnet_hdr=, "
"queues=, and vhostfds= are invalid with helper="
--Stefan]

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1431691143-1015-16-git-send-email-armbru@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 22 insertions, 23 deletions

diff --git a/net/tap.c b/net/tap.c
index c1ee4f1233..d1ca314dcf 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -713,7 +713,6 @@ static int get_fds(char *str, char *fds[], int max)
 int net_init_tap(const NetClientOptions *opts, const char *name,
                  NetClientState *peer, Error **errp)
 {
-    /* FIXME error_setg(errp, ...) on failure */
     const NetdevTapOptions *tap;
     int fd, vnet_hdr = 0, i = 0, queues;
     /* for the no-fd, no-helper case */
@@ -731,7 +730,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
     /* QEMU vlans does not support multiqueue tap, in this case peer is set.
      * For -netdev, peer is always NULL. */
     if (peer && (tap->has_queues || tap->has_fds || tap->has_vhostfds)) {
-        error_report("Multiqueue tap cannot be used with QEMU vlans");
+        error_setg(errp, "Multiqueue tap cannot be used with QEMU vlans");
         return -1;
     }
 
@@ -739,15 +738,15 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
             tap->has_vnet_hdr || tap->has_helper || tap->has_queues ||
             tap->has_fds || tap->has_vhostfds) {
-            error_report("ifname=, script=, downscript=, vnet_hdr=, "
-                         "helper=, queues=, fds=, and vhostfds= "
-                         "are invalid with fd=");
+            error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
+                       "helper=, queues=, fds=, and vhostfds= "
+                       "are invalid with fd=");
             return -1;
         }
 
         fd = monitor_fd_param(cur_mon, tap->fd, &err);
         if (fd == -1) {
-            error_report_err(err);
+            error_propagate(errp, err);
             return -1;
         }
 
@@ -759,7 +758,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
                          script, downscript,
                          vhostfdname, vnet_hdr, fd, &err);
         if (err) {
-            error_report_err(err);
+            error_propagate(errp, err);
             return -1;
         }
     } else if (tap->has_fds) {
@@ -770,9 +769,9 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
             tap->has_vnet_hdr || tap->has_helper || tap->has_queues ||
             tap->has_vhostfd) {
-            error_report("ifname=, script=, downscript=, vnet_hdr=, "
-                         "helper=, queues=, and vhostfd= "
-                         "are invalid with fds=");
+            error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
+                       "helper=, queues=, and vhostfd= "
+                       "are invalid with fds=");
             return -1;
         }
 
@@ -780,8 +779,8 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
         if (tap->has_vhostfds) {
             nvhosts = get_fds(tap->vhostfds, vhost_fds, MAX_TAP_QUEUES);
             if (nfds != nvhosts) {
-                error_report("The number of fds passed does not match the "
-                             "number of vhostfds passed");
+                error_setg(errp, "The number of fds passed does not match "
+                           "the number of vhostfds passed");
                 return -1;
             }
         }
@@ -789,7 +788,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
         for (i = 0; i < nfds; i++) {
             fd = monitor_fd_param(cur_mon, fds[i], &err);
             if (fd == -1) {
-                error_report_err(err);
+                error_propagate(errp, err);
                 return -1;
             }
 
@@ -798,7 +797,8 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
             if (i == 0) {
                 vnet_hdr = tap_probe_vnet_hdr(fd);
             } else if (vnet_hdr != tap_probe_vnet_hdr(fd)) {
-                error_report("vnet_hdr not consistent across given tap fds");
+                error_setg(errp,
+                           "vnet_hdr not consistent across given tap fds");
                 return -1;
             }
 
@@ -807,15 +807,15 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
                              tap->has_vhostfds ? vhost_fds[i] : NULL,
                              vnet_hdr, fd, &err);
             if (err) {
-                error_report_err(err);
+                error_propagate(errp, err);
                 return -1;
             }
         }
     } else if (tap->has_helper) {
         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
             tap->has_vnet_hdr || tap->has_queues || tap->has_vhostfds) {
-            error_report("ifname=, script=, downscript=, and vnet_hdr= "
-                         "queues=, and vhostfds= are invalid with helper=");
+            error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
+                       "queues=, and vhostfds= are invalid with helper=");
             return -1;
         }
 
@@ -832,13 +832,13 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
                          script, downscript, vhostfdname,
                          vnet_hdr, fd, &err);
         if (err) {
-            error_report_err(err);
+            error_propagate(errp, err);
             close(fd);
             return -1;
         }
     } else {
         if (tap->has_vhostfds) {
-            error_report("vhostfds= is invalid if fds= wasn't specified");
+            error_setg(errp, "vhostfds= is invalid if fds= wasn't specified");
             return -1;
         }
         script = tap->has_script ? tap->script : DEFAULT_NETWORK_SCRIPT;
@@ -853,15 +853,14 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
 
         for (i = 0; i < queues; i++) {
             fd = net_tap_init(tap, &vnet_hdr, i >= 1 ? "no" : script,
-                              ifname, sizeof ifname, queues > 1, &err);
+                              ifname, sizeof ifname, queues > 1, errp);
             if (fd == -1) {
-                error_report_err(err);
                 return -1;
             }
 
             if (queues > 1 && i == 0 && !tap->has_ifname) {
                 if (tap_fd_get_ifname(fd, ifname)) {
-                    error_report("Fail to get ifname");
+                    error_setg(errp, "Fail to get ifname");
                     close(fd);
                     return -1;
                 }
@@ -872,7 +871,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
                              i >= 1 ? "no" : downscript,
                              vhostfdname, vnet_hdr, fd, &err);
             if (err) {
-                error_report_err(err);
+                error_propagate(errp, err);
                 close(fd);
                 return -1;
             }